1. Field of the Invention
The present invention relates to a pattern forming method and, more particularly, to a pattern forming method and an electric device fabricating method using the same having a simple low cost process.
2. Description of the Background Art
In general, the pattern process of a semiconductor device is a critical factor in determining the performance and capacity of a device as well as in determining the spatial characteristics of the device. Efforts have been made to improve the performance of the semiconductor device. Research is actively ongoing especially to enhance the performance of the semiconductor device by forming a fine metal pattern (circuit pattern). A pattern forming process is not exclusively performed on the semiconductor device. A pattern forming process can also be used for a printed circuit board or a flat panel display device, such as a liquid crystal display device or a plasma display panel (PDP).
The most effective pattern forming process known so far is a process using a photoresist. FIGS. 1A to 1F illustrate sequential processes of a pattern forming method in accordance with the related art using a photoresist. As shown in FIG. 1A, photoresist, such as a photosensitive material, is deposited on a metal layer 3 formed on a substrate 1 made of an insulating material, such as glass or a semiconductor material, to form a photoresist layer 5.
Next, as shown in FIG. 1B, the photoresist layer 5 is baked. Subsequently, as shown in FIG. 1C, a mask 7 is positioned on the photoresist layer 5 and irradiated with a light, such as an ultraviolet light. In general, a photoresist can either be a positive photoresist or a negative photoresist. As an example, the case of a negative photoresist will be described for explanation purposes.
When the photoresist layer is irradiated with a light, the photoresist of the region, which is irradiated with the light, is changed in its chemical structure, so that when a developer is applied thereto, the photoresist of the region, which is not irradiated with the light, is removed to form a photoresist pattern 5a, as shown in FIG. 1D. And then, as shown in FIG. 1E, after an etching solution is applied to the photoresist pattern 5a and the metal layer 3, a metal pattern 3a under the photoresist pattern 5a remains because the photoresist pattern 5a blocks the etching solution from etching a portion of the metal layer 3 under the photoresist pattern 5a. Thereafter, as shown in FIG. 1F, when the photoresist pattern 5a is removed by applying a stripper, only the metal pattern 3a remains on the substrate 1.
The metal pattern forming method using a photoresist has several problems. First, the fabrication process is complicated. For example, the photoresist pattern is formed through photoresist deposition, baking, exposing and developing processes. To bake the photoresist, the photoresist needs to undergo a soft baking process carried out at a specific temperature and a hard baking process carried out at a higher temperature than the soft baking temperature, which makes the process more complicated.
Second, fabrication costs are expensive. Usually, in the fabrication of electronic devices including a plurality of patterns (or electrodes), such as a transistor, one photoresist process forms one pattern and another photoresist process forms another pattern. An expensive photoresist process line is required for each patterning process. Thus, fabrication costs of an electronic device increase for every patterning process required. For example, in the fabrication of a thin film transistor, the expense of the patterning process using a photoresist accounts for about 40˜45% of the total expense.
Third, patterning with a photoresist can cause environmental pollution if not properly treated. In general, photoresist is deposited by spin coating, which means that a lot of photoresist is discarded during deposition. Discarding of photoresist also increases fabrications costs of electronic devices in terms of material costs.
Fourth, resulting electronic products may be defective. For example, the thickness of a photoresist layer applied by spin coating can not be accurately controlled. A resultant photoresist layer may have a non-uniform thickness. Thus, non-stripped photoresist may end up remaining on the surface of a pattern after a patterning process such that a defective electronic device results.